fix: consider deficit as part of unbacked

this patch, prevent termporarily overpaying liquidity providers while the deficit is not resolved

fix: add tests to check ir invariants

fix: move update rates

docs/3.3/Aave-v3.3-features.md

@@ -160,3 +160,7 @@ We plan on adding more dedicated getters in the future as we see fit.
 
 The previously deprecated `pool.getReserveDataExtended()` was removed.
 You can fetch the data via `pool.getReserveData()`, `pool.getVirtualUnderlyingBalance()` & `pool.getVirtualUnderlyingBalance()`.
+
+While the interface of `calculateInterestRates` did not change, the usage assumptions changed.
+Instead of passing `reserve.unbacked` you now have to pass `reserve.deficit + reserve.unbacked`.
+The rational being that both values represent unbacked tokens on the pool.

docs/3.3/Aave-v3.3-properties.md

@@ -19,6 +19,7 @@ Formal properties in natural language of the 3.3 features.
 - Deficit added during the liquidation can't be more than the user's debt
 - Deficit can only be created and eliminated for an `active` reserve.
 - Edge case: deficit can be created and eliminated even is a reserve is `paused` in case it is not the main liquidated asset. Both actions don't affect a user negatively, and preventing the burning of bad debt on paused reserves could create overhead for the protocol.
+- For the interest rate calculation, deficit is treated equally as the unbacked parameter, given that it should be reducing utilisation.
 
 ### 2. Liquidation mechanics
 

src/contracts/protocol/libraries/logic/LiquidationLogic.sol

@@ -124,9 +124,6 @@ library LiquidationLogic {
       : IERC20(params.asset).balanceOf(msg.sender);
     require(balanceWriteOff <= userBalance, Errors.NOT_ENOUGH_AVAILABLE_USER_BALANCE);
 
-    // update ir due to updateState
-    reserve.updateInterestRatesAndVirtualBalance(reserveCache, params.asset, 0, 0);
-
     if (reserveCache.reserveConfiguration.getIsVirtualAccActive()) {
       // assets without virtual accounting can never be a collateral
       bool isCollateral = userConfig.isUsingAsCollateral(reserve.id);
@@ -163,6 +160,8 @@ library LiquidationLogic {
 
     reserve.deficit -= balanceWriteOff.toUint128();
 
+    reserve.updateInterestRatesAndVirtualBalance(reserveCache, params.asset, 0, 0);
+
     emit DeficitCovered(params.asset, msg.sender, balanceWriteOff);
   }
 

src/contracts/protocol/libraries/logic/ReserveLogic.sol

@@ -179,7 +179,7 @@ library ReserveLogic {
       reserve.interestRateStrategyAddress
     ).calculateInterestRates(
         DataTypes.CalculateInterestRatesParams({
-          unbacked: reserve.unbacked,
+          unbacked: reserve.unbacked + reserve.deficit,
           liquidityAdded: liquidityAdded,
           liquidityTaken: liquidityTaken,
           totalDebt: totalVariableDebt,